Heat-stable alkaline phosphatase in uterine cancer, with special reference to its histochemical heat-stability and the L-phenylalanine inhibition test.

We report a histochemical study of alkaline phosphatase (ALP) in normal cells of the female reproductive system, in pre-cancerous and cancerous lesions of the uterine cervix and in endometrial cancer to ascertain the incidence of ALP and its isoenzyme type. For this purpose, serial sections were subjected to heat stability and L-phenylalanine (LP) inhibition tests. The Regan-like isoenzyme, a heat-stable and LP-sensitive ALP, which has been thought to derive only from cancer or the placenta, was found in uterine cervical reserve cells and endometrial luminal surface lining cells. In contrast, ALP activity in endometrial glandular cells was found to be heat and LP sensitive. Of 183 cases of cervical neoplasia, 60 (33%) manifested non-specific ALP activity. One dysplasia and two invasive cancer cases manifested the Regan-like isoenzyme. The other 36 classifiable lesions had small-intestine ALP-like activity (marked heat and LP sensitivity) or a liver ALP-like isoenzyme (marked heat and slight LP sensitivity). Of 42 cases of endometrial cancer, all cases manifested non-specific ALP activity. Seven endometrial cancers exhibited the Regan-like isoenzyme. The other 19 cases manifested either small intestine or liver ALP-like isoenzyme. Our findings indicate that in the course of uterine carinogenesis, the ALP isoenzyme of reserve cell and endometrial glandular cells undergo a change and that enzyme deviation occurs.